The present invention is directed to an optical system or apparatus for improving the center beam candle power seconds (axial intensity) and zonal lumen seconds (field illumination) of a flash lamp in a photoflash unit. This is accomplished with the use of a unique lens and reflector system for in particular providing an improvement in light distribution.
The use of a lens in association with a source and reflector can be found in early patents relating to lighting apparatus such as U.S. Pat. No. 1,805,690 (Dodge). The product illustrated in U.S. Pat. No. 1,805,690 employs a relatively large reflector in comparison with the light source and the lens. The apparatus is particularly described as one for controlling lateral divergence. The lens in this patent is connected directly to the light source (as part of the lamp's envelope) and not directly associated with the reflector. Examples of multilamp photoflash units employing prismatic light controlling means are shown in U.S. Pat. Nos. 3,993,896 (Wacker), 3,995,149 (Lukas), and 4,172,273 (Schilling, et al). The units described in these patents employ a forwardly disposed prism. The prism construction employed is substantially flat and, although it does provide some degree of light level distribution, there is a tendency, as mentioned in U.S. Pat. No. 4,172,273, to produce an intensity dip at the pattern center U.S. Pat. No. 3,993,896 employs a prism arrangement for compensating for lateral spreading of the light rays. However, none of the aforementioned patents provide a degree of improvement possible with the construction of the present invention, particularly the improvement of the center beam characteristics evidenced by the maintenance of a substantially uniform light distribution even at a substantial off-center deviation.